Steve Blum and Fred Tatasciore in Hulk Vs. (2009)
went berserk during his duel against the Hulk
*berserkers were ancient Norse warriors, known for the ability to get into uncontrollable rage before battle, which allowed them to fight with great strength and bloodlust, while also giving them immunity to fear and pain (thus giving rise to a modern term 'to go berserk')
Related poll: Big screen berserkers
Thanks to yrnej for some suggestions
went berserk during his duel against the Hulk
went berserk during a battle between the armies of Earl Ragnar and Jarl Borg
goes berserk during a lot of her fights
goes berserk whenever her alter-ego JESSICA appears
went berserk during his battle against the beetle drones
went berserk on Memmio, by ripping out his tongue with his mouth
goes berserk during the games of dodgeball, whenever an opponent calls him 'Frenchy'
went berserk after a group of Klansmen vandalized Mindy's home
went berserk on a cow, after getting very hungry
goes berserk whenever Catherine is put in danger
went berserk on George Luiquor, in a banned episode Man's Best Friend (2003)
went berserk while being held captive by Darken Rahl
went berserk when Raditz bested his father, Goku
went berserk on Oberyn Martell's face
goes berserk whenever a Little Sister is threathened
went berserk on George 'The Reaper' Foyet
went berserk on The Joker after Robin was indoctrinated
went berserk when he found out who poisoned Brock
went berserk on the people who killed Rin Nohara
went berserk on Joe's throat, while him and his group were being molested
went berserk during his assault on the arsenal of Istanbul
went berserk on band of thugs (beating them with food cans) after they molested his family
went berserk during his duel against Frieza
went berserk during the off-screen battle against the Ottomans (where he single-handedly defeated a Turkish horde with nothing but a fruit-peeling knife)
went berserk during his 1 vs 100 battle against Adon's soldiers
went berserk on Zeltrax and his giant monster, while being taunted by them
goes berserk while doing his endless Leg Beatdown fatality
went berserk when he got a hold of the Berserker Staff
goes berserk whenever he enters his beast form
went berserk on Beta Ray Bill's face
goes berserk countless times, during his quest for revenge
went berserk during his duel against Asajj Ventress
went berserk during his fight against the Hulk
went berserk when he charged at Mannoroth
went berserk during an episode of The $10,000 Pyramid (1973) (watch the scene here)